Plain bearing failure index

8.0 Electrical damage

Electrical Damage Index


8.2 Electrical Erosion Damage in Journal Bearing (2)

Click on photograph to enlarge
	Spark erosion damage on top half of ring-oil bearing
Main Characteristics	Note the characteristic roughening at the leading edge of the top half bearing. In this case so much damage had been caused to the bottom half that it had wiped and the evidence of electrical damage had been removed.
Cause	Electrical fault in motor causing sparking through oil film at area of minimum film thickness.
Note	Evidence of electric arcing was also present on journal
Possible Confusion with Other Types of Damage	Dirt erosion (see Erosion of White Metal Journal Bearing) and cavitation erosion give a superficially similar matt finish on the bearing surface, but both of these have an arrow shape pointing against direction of motion. Moreover, there is no corresponding damage on the journal
Comment	This was the third successive failure to the motor after an overhaul. The wiping in the first two was attributed to lubricant breakdown caused by dirt in the oil; this was also considered responsible for the damage to the journal. A more careful examination after the third failure revealed the erosion damage on the top half bearing and that the damage to the journal was pitting, not scoring.

Services Index
Site Map
Home page